He is critical of string theory on the grounds that it lacks testable predictions and is promoted with public money despite its failures so far,[1] and has authored both scientific papers and popular polemics on this topic. His writings claim that excessive media attention and funding of this one particular mainstream endeavour, which he considers speculative, risks undermining public faith in the freedom of scientific research. His moderated weblog on string theory and other topics is titled "Not Even Wrong", a derogatory term for scientifically useless arguments invented by Wolfgang Pauli.

For the last eighteen years particle theory has been dominated by a single approach to the unification of the Standard Model interactions and quantum gravity. This line of thought has hardened into a new orthodoxy that postulates an unknown fundamental supersymmetric theory involving strings and other degrees of freedom with characteristic scale around the Planck length. […] It is a striking fact that there is absolutely no evidence whatsoever for this complex and unattractive conjectural theory. There is not even a serious proposal for what the dynamics of the fundamental 'M-theory' is supposed to be or any reason at all to believe that its dynamics would produce a vacuum state with the desired properties. The sole argument generally given to justify this picture of the world is that perturbative string theories have a massless spin two mode and thus could provide an explanation of gravity, if one ever managed to find an underlying theory for which perturbative string theory is the perturbative expansion.[5]